INTRODUCTION MATERIAL AND METHODS Laboratory

Annals of Warsaw University of Life Sciences – SGGW
Land Reclamation No 45 (2), 2013: 217–226
(Ann. Warsaw Univ. of Life Sci. – SGGW, Land Reclam. 45 (2), 2013)
Laboratory assessment of permeability of sand and biopolymer
mixtures
MATEUSZ WISZNIEWSKI1, ZDZISLAW SKUTNIK2, ALI FIRAT CABALAR1
1
Department
2
of Civil Engineering, University of Gaziantep
Department of Civil Engineering, Warsaw University of Life Sciences – SGGW
Abstract: Laboratory assessment of permeability
of sand and biopolymer mixtures. This research
presents a method of creating seepage barriers in
a sandy soil using biopolymer additives (biosubstance), which consist of polysaccharides and water. Polysaccharides strongly interact with water
to produce a viscous suspension. The paper aims
to investigate the influence of a biosubstance employed in a highly permeable sandy soil. Amount
of the biopolymer used in a sample were 0.5, 1.0
and 1.5%, by dry weight. The test results indicate
that the hydraulic conductivity significantly decrease with the amount of biosubstance added but
only slightly increase when curing time gets longer. It is thought that such application, which is
a relatively new soil improvement technique, could
be used as a seepage barrier installation required to
protect some geotechnical works including foundation, underground structures and waste disposals.
Key words: biopolymers, permeability, seepage
barrier
INTRODUCTION
Over the past years, many types of chemicals have been used for a geotechnical
application. Chemical grouts are mostly
toxic and hazardous for the environment.
This constantly pushes researchers to
find alternative eco-friendly techniques
of ground improvement. It comes to light
that several natural biopolymers have
important characteristics, such as excellent viscosifying in high-salinity waters,
pseudo plasticity, stability at large ranges
of temperature and pH, jellifying agents
and resistance to shear degradation.
The use of biopolymers for soil improvement is already described in readily available literature. Several studies
(Feldman 1989, Li et al. 1993, Martin et
al. 1996, Stewart and Fogler 2001) have
investigated the application of biopolymers as plugging agents in construction
of various impervious barriers. Some researchers (Karimi 1997, Momeni et al.
1999, Khachatoorian et al. 2003) demonstrated the capacity of certain biopolymers, including xanthan gum and sodium
alginate to decrease the permeability and
increase the shear strength, thus reduce
the leaching of contaminants.
While most of the investigations focus on fine, cohesive soil, the present
research analyzes the potential use of
biopolymer, namely xanthan gum, to reduce hydraulic conductivity of medium
grain size sand. This part of research
which should be regarded as a preliminary to investigate the influence of the
biopolymer content on the reduction of
the soil permeability.
MATERIAL AND METHODS
The materials used in the tests described
in this paper were quartz medium sand
and xanthan gum. The commercially
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M. Wiszniewski, Z Skutnik, A.F. Cabalar
available sand was obtained from regional sources near Warsaw. The specific gravity of the grains was found to
be 2.68. A gradation of the sand falling
between 1.00 and 0.071 mm was artificially selected. The grain size distribution curve of medium sand taken for the
investigations is presented in Figure 1,
while index properties of this soil in Table 1.
from the bacteria Xanthomonas campestris. Xanthan gum is as a hydrophilic
colloid to thicken and stabilize water-based suspensions. It is widely used in
the drilling industry to thicken drilling
fluids, and is very stable under various
values of temperature and pH (Bouazza
et al. 2009).
Samples were prepared by mixing
sandy soil with xanthan gum by dry
FIGURE 1. Particle size distribution curve
TABLE 1. Index properties of the sand
Property
Value
Minimum void ratio, emin
0.45
Maximum void ratio, emax
0.70
Relative density, RD
45%
Uniformity coefficient, Cu
1.96
Curvature coefficient, Cc
0.84
Soil contains rectangular quartz
grains with coefficient of uniformity
– Cu = 1.96 and coefficient of curvature
– Cc = 0.84.
The commercially available biopolymer material was obtained from a local
food store in a powder form. Worldwide
production of xanthan gum comes out
weight. Four different mixtures were
prepared, containing respectively 0.0,
0.5, 1.0 and 1.5% of biopolymer. The
required amounts of sandy soils and xanthan gum were blended together under
dry conditions. Firstly sand was washed
and dried in an oven at approximately
105°C. For all the tests samples were
prepared at relative density 45%.
For the initial sand-xanthan gum-water specimen, the desired amount of the
sand and xanthan gum were weighed,
mixed, water was added, reaching 10%
of each dry sample weight and then all
was spooned, without vibration, into the
mould (with a diameter of 69 mm, and
height of 70 mm) with thin layers of
Laboratory assessment of permeability of sand and biopolymer mixtures
sand. When the mould was completely
filled, using plastic bags and foil it was
tightly sealed to prevent moisture loose.
Then samples were left for conditioning,
respectively for 1, 3, 7, 14, and 28 days
of time. Permeability apparatus with the
specimen can be seen in Figures 2 and 3.
The permeability tests were conducted on clean sands and sand with xanthan
gum at three different contents. A series
219
of constant head permeability tests were
performed according to ASTM D2434.
Tests were conducted in a triaxial cell,
where hydraulic gradient and confining
pressure were controlled (Lipiński et
al. 2007). All samples were made saturated from the bottom to top. Pressure
at the top of each sample was set to be
0 kPa, while at the bottom applied pressure took values of 5, 10, 20, 30, 50 and
FIGURE 2. Permeability apparatus: 1 – specimen; 2 – triaxial cell, 3 – cell pressure controller; 4 – pore
water controller; 5 – out-flow cylinder; 6 – sample mould
100 kPa (Head 1995). Confining pressure in the cell was set to be 50 kPa (for
bottom pressure of 5, 10, 20 and 30 kPa),
100 kPa (for 50 kPa) and 200 kPa (for
100 kPa). The hydraulic conductivity of
each sample was reported by the average
of the last three measurements. All tests
were conducted under room temperature
(22°C).
RESULTS AND DISCUSSIONS
FIGURE 3. Permeability cell
The testing results on hydraulic conductivity of biopolymer treated sand are
shown in Table 2. Permeability (hydraulic conductivity) decreases when more
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M. Wiszniewski, Z Skutnik, A.F. Cabalar
TABLE 2. Hydraulic conductivity of biopolymer treated sand for various curing time
Biopoly- Curing
mer ratio time
[%]
[days]
1
0.5
1.0
1.5
Permeability [m/s]
Pressure applied [kPa]
5
10
–10
8.65·10
–10
20
–10
30
–8
9.02·10
1.13·10
–9
–8
50
–8
8.71·10
–7
100
–7
1.55·10–6
–6
5.25·10
3
6.26·10
2.42·10
5.30·10
3.76·10
1.33·10
1.83·10–6
7
4.25·10–9
4.42·10–9
9.89·10–8
9.75·10–7
1.45·10–6
2.14·10–6
14
3.12·10–9
4.92·10–8
2.80·10–7
7.49·10–7
1.68·10–6
2.35·10–6
28
3.14·10
–8
–7
–7
1.53·10
–6
2.67·10
–6
2.59·10–6
1
3
3.68·10
7
4.98·10–10
5.54·10–10
–9
–9
2.03·10
9.02·10
1.18·10–10
1.24·10–10
4.67·10–10
7.23·10–10
7.12·10–9
1.98·10–7
–10
–10
–10
2.75·10
–9
1.79·10
–8
9.09·10–7
6.74·10–10
3.81·10–9
3.75·10–8
1.29·10–6
–8
7.17·10
–8
4.09·10
–7
1.42·10–6
14
2.12·10
28
3.94·10
7.07·10
2.64·10
1.47·10
2.69·10–9
2.50·10–9
5.56·10–9
2.00·10–7
3.34·10–7
1.03·10–6
–11
–11
–10
–10
5.08·10
–11
9.25·10–8
1
2.84·10
3
7
4.39·10
14
28
7.33·10
1.28·10
2.20·10
3.40·10–11
3.38·10–11
1.54·10–10
7.53·10–11
2.59·10–11
7.90·10–8
–11
–11
–11
–11
–11
3.90·10
7.73·10
4.91·10
3.20·10
1.41·10–7
2.18·10–11
2.51·10–11
1.20·10–10
7.98·10–10
2.70·10–10
6.39·10–7
6.84·10–11
5.69·10–11
2.80·10–10
7.27·10–10
8.66·10–10
1.99·10–7
xanthan gum is added to the sample. For
example, addition of just 0.5% xanthan
gum to the sand decreases the permeability to almost 0.001% of the initial value.
Addition of 1.5% xanthan gum changes
the permeability from 8.46 · 10–5 m/s to
about 2.84 · 10–11m/s, which is less than
1,000,000 times.
Figure 4 presents three graphs with
different xanthan gum (biopolymer) content, where the changes of permeability,
according to the hydraulic gradient applied for various curing time are shown.
It is seen that hydraulic conductivity increases as the applied pressure increases,
and as the curing time gets longer. Permeability of the specimens remains low, under greater hydraulic gradient for higher
xanthan gum ratio. As presented in the
graph for 1.5% biopolymer content, wa-
ter flow through the sand is stable, for all
the samples (different curing times) for
a hydraulic gradient up to 70. In that case
improved sand might be considered as
impermeable, reaching values between
2.18 · 10–11 and 8.66 · 10–10 m/s.
Effect of time on hydraulic conductivity of the soil biopolymer mix under
various pressures is shown in Figure 5.
When the long-term behavior of seepage
barriers is a main objective, observing
short-term behavior is a good evidence
of the possible technology development.
A longer ageing time generally achieved
a lower conductivity, but work with
coarse and medium sand shows different relationship (Fig. 5). It can realized
that the permeability (hydraulic conductivity) of a biopolymer treated sand increases with time, for the 0.5% mixture
Laboratory assessment of permeability of sand and biopolymer mixtures
FIGURE 4. Hydraulic conductivity of a biopolymer treated sand
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FIGURE 5. Effect of time on hydraulic conductivity of the soil biopolymer mix
Laboratory assessment of permeability of sand and biopolymer mixtures
FIGURE 6. Effect of biopolymer content on hydraulic conductivity of the soil
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M. Wiszniewski, Z Skutnik, A.F. Cabalar
under pressure of 30 kPa, it increases from
3.76 · 10–7 m/s at 3 days to 1.53 · 10–6 m/s
at 28 days. The ageing influence gets
lower, when the xanthan gum content increases, for 1.5% mixture under pressure
of 30 kPa, it increases from 7.53 · 10–11 m/s
at 3 days to only 7.27 ·10–10 m/s at 28
days. Permeability remains low and stable for all 28 days, up to the hydraulic
gradient value of 70.
A polymerc chain is significant for
permeation of the grout. When the biopolymer is placed in the soil matrix, it is
desired to undergo some form of cross-linking in order to enhance strength
and decrease its mobility in the ground.
Cross-linking connects polymeric chains
through chemical reactions, which might
be initiated by temperature rise, change
in pressure and pH. The process can
form a comprehensive lattice in the soil
matrix, which rigidifies the whole polymeric structure, enhance its mechanical
strength and reduce permeability (Khatami and O’Kelly, 2012).
As the effect of the biopolymer inclusion, stable permeability decrease was
observed as shown in Figure 6. When the
biopolymer ratio increases permeability
decreases of no account of conditioning
time and pressure applied. It determines
a possible usage of that chemical material
to create impervious barriers in the soil.
Viscous characteristics of xanthan
gum have a significant meaning for stability of the soil. As observed in Figure
7, samples mixed with the xanthan gum
appeared to be much more stable. The
sand grains sticked to each other, and
created a linked structure. That gives
another conceivable way to use of such
products in the ground, for instance in
slope or road embankment stability.
FIGURE 7. Rigid samples after testing
CONCLUSIONS
The objective of the presented study was
to investigate the behavior of sandy soil
and its various mixtures with xanthan
gum in the terms of hydraulic conductivity. It is known that biopolymers (i.e.
xanthan gum) can substantially decrease
hydraulic conductivity (permeability) of
soil without causing environmental toxicity.
Based on the test results which was
the first part of research to investigate the
influence of the biopolymer content on
the reduction of the soil permeability it
was proved that the permeability of medium sand treated with xanthan gum was
found to be directly dependent on the
biopolymer concentration.
However, on the basis of the test results the effect of curing time on changes
in soil permeability cannot be fully assessed. A longer ageing time generally
achieved a lower conductivity.
Also more detailed research is required to impact assessment of pore
water pressure (hydraulic gradient) on
hydraulic conductivity of sand-xanthan
gum-water specimen.
In conclusion, biopolymer treatment
occurs to be a promising technology to
Laboratory assessment of permeability of sand and biopolymer mixtures
modify an engineering soils behavior.
The eco-friendliness and cost of biopolymers also add to their attractiveness for
use in engineering applications.
However, further studies are needed
for better understanding of the use of
different biopolymers and percentages
with various types of soils. The future
research will assess the sustainability of
the changes in the structure of the soil,
as a result of moisturizing-drying cyclicality, which seems to be crucial in the
use of the method in hydro-engineering
constructions. Mechanical testing of the
shear strength in triaxial apparatus and
oedometer compressibility tests have
been started.
REFERENCES
ASTM D 2434-94, 2000: Standard Test
Method for Permeability of Granular
Soils (Constant Head). Annual Book of
ASTM Standards, American Society For
Testing and Materials, West Conshohocken, PA, 04.08.
BOUAZZA A., GATES W.P., RANJITH P.G. 2009: Hydraulic conductivity
of biopolymer treated silty sand. Géotechnique 59(1): 71–72.
FELDMAN D. 1989: Polymeric Building
Materials. Elsevier Science,
HEAD K.H., 1995: Manual of soil laboratory
testing. Vol. 2. Pentech Press, London.
KARIMI S. 1997: A study of Geotechnical Applications of Biopolymer Treated
Soils with an Emphasis on Silt. Phd
Thesis, Civil Engineering Department,
University of Southern California, Los
Angeles, CA.
KHACHATOORIAN R., PETRISOR I.G.,
KWAN C.C., YEN T.F. 2003: Biopolymer plugging effect: laboratory-pressurized pumping flow studies. J. Pet. Sci.
Engng. 38(1–2): 13–21.
225
KHATAMI H.R., O’KELLY B.C. 2012: Improving mechanical properties of sand
using biopolymers. Journal of Geotechnical and Geoenvironmental Engineering
LI Y., YANG I.C.Y., LEE K.-I., YEN T.F.
1993: Subsurface application of Alcaligenes eutrophus for plugging of porous media. E.T. Premuzic, A.Woodhead
(Eds.). Microbial Enhanced Oil Recovery
- Recent Advances. Amsterdam: 65–77.
LIPIŃSKI M., KODA E., WDOWSKA M.
2007: Laboratory assessment of permeability of a groundwater protective barrier. Annals of Warsaw University of Life
Sciences, Land Reclamation 30: 69–79.
MARTIN G.R., YEN T.F., KARIMI S. 1996:
Application of biopolymer technology
in silty soil matrices to form impervious
barriers. Proceeding of 7th Australia-New
Zealand Geomechanics Conference. Adelaide, Australia.
MOMENI D., KAMEL R., MARTIN G.R.,
YEN T.F. 1999: Potential use of biopolymer grouts for liquefaction mitigation.
A. Leeson, B.C. Alleman (Eds.). Phytoremediation and Innovative Strategies
for Specialized Remedial Applications 5
(6): 175–180.
STEWART T.L., FOGLER H.S. 2001: Biomass plug development and propagation
in porous media. Biotechnology and Bioengineering 5: 353–363.
Streszczenie: Ocena przepuszczalności mieszaniny piasku i biopolimeru na podstawie badań
laboratoryjnych. Przedstawione badania dotyczą możliwości tworzenia nieprzepuszczalnych
barier w przepuszczalnym podłożu gruntowym
z zastosowaniem dodatków biopolimeru (biosubstancji składającej się z polisacharydów i wody)
mieszanych z piaszczystym gruntem podłoża. Celem przeprowadzonych badań była ocena wpływu
biopolimeru na przewodność hydrauliczną piasku
średniego. Badania przeprowadzono dla zawartości biopolimeru 0,5, 1,0 i 1,5% w odniesieniu
do suchej masy piasku średniego i różnych wartości gradientów hydraulicznych. Wyniki badań
wskazują, że przewodność hydrauliczna znacząco zmniejsza się wraz ze wzrostem zawartości
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M. Wiszniewski, Z Skutnik, A.F. Cabalar
biopolimeru, jednakże nieznacznie wzrasta
w miarę wydłużania się czasu kondycjonowania.
Zastosowanie biopolimeru do tworzenia nieprzepuszczalnej bariery hydraulicznej jest stosunkowo nową techniką, którą można wykorzystać
w niektórych pracach geotechnicznych, np. do
zabezpieczania wykopów fundamentowych lub
składowisk odpadów.
Słowa kluczowe: biopolimery, przepuszczalność,
bariera przeciwfiltracyjna
MS. received December 2013
Authors’ addresses:
Mateusz Wiszniewski, Ali Firat Cabalar
University of Gaziantep
Department of Civil Engineering
27310 Gaziantep, Turkey
e-mail: [email protected]
Zdzisław Skutnik
Wydział Budownictwa i Inżynierii Środowiska
Katedra Inżynierii Budowlanej
ul. Nowoursynowska 159
02-776 Warszawa
Poland
e-mail: [email protected]